Energy is the correct answer
You're pretty close. It's all in the details.
A. Correct.
B. Correct.
C. Sign error in the boxed answer. -(-0.5) = 0.5
The graph shows c ≈ 1.855. If a is more than that and decreasing, area is increasing. The sign of dA/dt will be positive. (Compare to D)
D. Units are not shown. Numerical value is correct.